GalvInfo Center
Inquiries about Construction and Appliance
Applications of Zinc-Containing Coated Steel
SheetTrends and Implications
Presented at Galvatech ‘04April 4-7, 2004
Chicago, Ill
GalvInfo Center
A zinc-coated steel sheet technical information center
managed by ILZRO and cosponsored by the steel, paint
and zinc industries.
GalvInfo Center
Objectives Provide technical assistance to users and
potential users of zinc and zinc-alloy coated steel sheet
Broaden the understanding of the user community about behavior and performance of coated steel sheet
Assist with growing the markets for zinc
and zinc-alloy coated steel sheet
GalvInfo CenterSPONSORS - 2004
American Zinc Association GE Betz Henkel Surface Technologies IMCO Recycling International Steel Group InterAmerican Zinc International Zinc Association PPG Steelscape The Techs USS-POSCO
GalvInfo Center Inquiry Topics - 2003
Construction83%
Corrosion47%
Service Life35%
In the atmosphere – 9%
In buildings – 8%
With treated wood – 8%
In concrete – 4%
Galvanic contact – 4%
In soil – 2%
Various12%
Storage stain – 6%
Salt spray resistance – 4%
Zinc runoff – 2%
Appearance20%
Phosphatizing – 6%
Painting issues – 6%
Dulling and others – 8%
Weldability11%
General – 5%
Galvalume – 2%
Phosphatized – 2%
To stainless – 2%
General6%
Coating thickness – 4%
Fire ratings – 2%
Appliance17%
Coatings11%
Salt spray testing – 2.5%
HDG versus EG versus Galvalume – 2.5%
Coating weight versus performance – 2%
Heat resistance – 2%
Prepaint – 2%
Formability – 2%; Specifications – 2%; Passivation – 2%
Corrosion Inquiries
Service life Atmospheric (indoors & outdoors) In concrete In contact with treated wood Dissimilar metal contact In soil and marine environments
Storage stain & salt spray Zinc runoff
Atmospheric Service Life
Atmospheric - Indoors
Source: CSSBI
Atmospheric - Indoors
Galvanize for lightweight steel framing (LSF) Corrosion rate < 0.1 microns/year
Necessity for G90 for indoor use? Study LSF use in actual buildings Develop database – life vs. environment
Use of lighter coating weights in appliances and electronic cabinetry
Contact with Concrete
Source: SIMPSON Strong-Tie
Contact with Concrete
Corrosion rate of galvanize imbedded in concrete is <0.1 microns/year if: Water/cement ratio <0.6 Chloride content <1%
Not widely understood that chemistry of concrete can affect galvanize life
Advise no contact between 55% Al-Zn coated sheet and concrete
Contact with Treated Wood
Source: SIMPSON Strong-Tie
Contact with Treated Wood
Wood preservative change results in increased corrosion of galvanized connectors CCA-C changed to ACQ-C, ACQ-D, CBA-A, CA-B
AC-D and CA-B over twice as corrosive as CCA-C due to higher Cu content
G60 and G90 satisfactory in past Move to G185 or to stainless steel Study required to reduce corrosiveness of
new treatments
Dissimilar Metal Contact
Galvanic Corrosion Rates – Zinc Coupled to Other Common Metals
CoupledAlloy
Galvanic Corrosion Rate (m/yr)
Rural Urban Marine
Zinc freely exposed
0.5 2.4 1.3
Mild steel 3.0 3.3 3.9
Stainless Steel 1.1 1.8 2.0
Copper 2.2 2.0 3.2
Aluminum 0.4 1.1 1.1
Soil & Marine Environments
Soil & Marine Environments
Soil Inhomogeneous – data not available for
many situations Most recent large study – 1955
Marine Large variability in corrosion rates
depending on location and water type Heaviest coating weights recommended
Storage Stain
Storage Stain
Storage stain is zinc hydroxide Most calls about how to remove
White stain – superficial and removable Black stain – damages coating
If removed – metallic sheen lost Many rejections for aesthetic reasons Restoration treatment needs to be
found
Salt Spray Testing
GalvInfoNote #15 covers most FAQs Does not predict service life Questions on hours to red rust
versus coating thickness
Zinc Runoff
Zinc Runoff
Some localities have adopted EPA guidelines on zinc levels in runoff water as regulations
Runoff model under study – results being presented at this conference
Indications are zinc levels drop before water reaches streams
Appearance Inquiries Bonderized (phosphatized) galvanize
Being used in unpainted state – despite uneven gray appearance
Need to develop a prepainted product that has Bonderized look
How to dull metallic sheen of galvanize
How to paint weathered/rusted galvanize
Weldability
How doe arc welding of 55% Al-Zn differ from that of galvanize
How to solder phosphatized galvanize How does spot welding affect
corrosion resistance of galvanzie GalvInfoNote on Weldability to be
issued
Passivation
Issue of hexavalent chromium becoming important Cr bearing passivation cannot be
guaranteed free of Cr+6
Demand for chromium-free passivation treatments will increase sharply
Other Inquiries
Temperature resistance of galvanize Use of 55% Al-Zn in cooking appliances Fire ratings Clarification of specifications Formability issues Where to purchase coated sheet
Summary Data base-actual corrosion of LSF Guide to coating weight selection of LSF Guide to use of galvanize in concrete Complete study of corrosiveness of new
wood preservatives Better methods of removing white rust Finalize zinc runoff studies Market for low-gloss architectural panels Deploy chrome-free passivation Obtain fire ratings for buildings using LSF
GalvInfo Center
Contact InformationWebsite: www.galvinfo.comE-mail: [email protected]: 888-880-8802Fax: 905-315-7442
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